1. Field of the Invention
The present invention relates to a liquid crystal display device that can be used in bidirectional image communication devices such as a TV phone, portable information terminal devices and various other types of video devices.
2. Description of the Related Art
In recent years, remarkable development of information communication networks has increased the necessity to develop bidirectional multi-media information communication devices for bidirectionally communicating image information such as motion pictures, still pictures and the like in addition to conventional information transmissions using sounds and characters. Various communication devices like TV phones have conventionally been used to bidirectionally communicate image information and audio information. Recently, it has become increasingly more common to transmit and receive via telephone lines video information recorded by a video camera.
However, such communication devices for bidirectionally communicating image information have the following problems. In bidirectionally communicating information using a conventional bidirectional image communication device such as a TV phone or the like, a user's eyes are directed to an image display section of the image communication device in which the image transmitted from the counterpart is displayed, however a camera section for capturing an image of the user cannot be disposed in a direction in which the user's eyes are directed. Therefore, the conventional bidirectional image communication device cannot present an image of one user in which the direction of his eyes coincides with the direction of the eyes of the other user.
In addition, in the case where an image input device which is generally used as a home-use video device is employed as a camera section for a bidirectionally image communication device, it is difficult to reduce the size of the image communication device. More specifically, as shown in FIG. 10, the above-mentioned image input device includes an optical system including: a lens 1; an iris 2; an IR cut filter 3; an optical lowpass filter 4; and a color filter 5, a charge coupled device (CCD) 6 and a signal/image processor 7 connected to the CCD 6. The color filter 5 is provided on the CCD 6. This image input device obtains color image information by reducing the size of an image entering from the lens 1 and projecting the image onto the CCD 6. Consequently, the optical system is indispensable to this image input device. However, in the case where this image input device is incorporated into a communication device, the optical system serves as a significant and undesirable obstacle to size reduction of the communication device.
In order to overcome the above-mentioned problems, Japanese Laid-Open Patent Publication No. 7-28095 discloses a liquid crystal display apparatus having image input devices. In the liquid crystal display apparatus, active devices used as switching devices for driving pixels are provided on one substrate, while the image input devices (each of which includes a photodiode and a MOS transistor) are provided on the other substrate, i.e., a counter substrate. However, in this liquid crystal display apparatus, it is necessary to use a transparent substrate as the counter substrate. When a glass substrate is used, the temperature in the fabrication process of the image input devices is limited to the upper limit of the heat-resistance of the glass substrate. This makes it difficult to form high performance image input devices on glass substrates. Alternatively, when a quartz substrate which is transparent and has a higher upper limit of heat-resistance is used, the temperature of the fabrication process of the image input devices is not limited. However, the quartz substrate increases the production cost of the entire liquid crystal display apparatus.